Enery Transfer

Question 1

How do plants use sugars

Answer 1

• primarily as respiratory substrates
• synthesis other biological molecules eg cellulose

Question 2

What is biomass

Answer 2

Total dry mass of tissue or mass of carbon measured over a given time in a specific area

Question 3

Units for biomass

Answer 3

When an area is being samples: gm-2
When a volume is being sampled: gm-3

Question 4

How u can’t ensure all water is removed from an sample

Answer 4

Heat the sample and reading it until the mass reading is constant

Question 5

Define gross primary production

Answer 5

Total chemical energy in plant biomass within a given volume or area

Question 6

Define net primary production

Answer 6

Chemical energy store in plant biomass after respiratory losses to the environment

Question 7

Mathematical equation timing NPP and GPP together

Answer 7

NPP = GPP - R ( respiratory losses)

Question 8

What is NPP available for

Answer 8

• Plant growth and reproduction
• other tropic levels in the ecosystem eg herbivores and decomposers

Question 9

How can biomass be measured

Answer 9

In terms of mass of carbon and dry mass of tissue per given area

Question 10

Method to measure biomass

Answer 10

• sample of organism ride in an oven set at low temp (avoids combustion)
• sample reweighed at egular intervals
• all water removed when mass remains constant
• mass of carbon taken to be 50% of dry mass

Question 11

Why is dry mass more representative

Answer 11

Water content of maples varies

Question 12

How can chemical energy stored in dry biomass be estimated

Answer 12

Using a calorimetry
- sample of dry mass burnt
- energy released is used to heat a known volume of water
- change in temp of water used to calculate the chemical energy

Question 13

What 3 groups are organism divided into

Answer 13

• producers
• consumers ( primary, secondary tertiary)
• saprobionts (decomposers)

Question 14

Why are orangisms divided in to groups and what is it based of

Answer 14

How they obtain their energy and nutrients

Question 15

What are tropic levels

Answer 15

Energy flows from primer producers to consumers

Question 16

What is lost with each trophic level

Answer 16

Energy

Question 17

What it’s is biomass measured in

Answer 17

• dry miss per given area in given time
• area of grassland per square metre/gm-2
• for volume grams per cubic metre gm-3

Question 18

Problems with measuring dry mass

Answer 18

• all organisms must be killed
• only a small sample can be taken may not be representative

Question 19

How can energy from burnt biomass be calculated

Answer 19

E = charge in temp/ specific heat capacity + volume

Question 20

What is NPP used for in plants

Answer 20

• plant growth and reproduction

Question 21

Explain why length of food chains is limited

Answer 21

Energy is lost at each trophic level
Insufficient energy to support higher trophic level

Question 22

Why is most of the sun energy not converted to organic matter

Answer 22

• most solar energy is absorbed by atmosphere or reflected by clouds
• photosynthetic pigments cannot absorb some wavelengths of light
• not all light falls directly on a chlorophyll molecule
• energy lost as heat during respiration/photosynthesis

Question 23

How can net reduction of consumers be calculated

Answer 23

N = I - (F+R)
I : chemical energy from ingested food
F :energy lost as faeces and urine
R: respiratory losses

Question 24

Why does biomass decrease long the food chain

Answer 24

• energy lost in nitrogenous waste (urine) and faeces
• some of the origins is not consumed
• energy lost to surrounding as heat

Question 25

What is primary ad secondary productivity

Answer 25

• Rate of primary or secondary production
• biomass in a specific area over a given time period eg Kj ha-1 year-1

Question 26

Common farming practise and how they increase efficiency of energy transfer

Answer 26

• exclusion of predators: no energy los to other organisms in food web
• artificial heating: reduce energy lost to maintain constant body temp
• restriction of movement : les energy lost in muscle contraction
• feeding controlled at the optimum : more growth less waste

Question 27

Equation for efficiency

Answer 27

Energy converted to a useful form (J) x 100/ total energy supplied

Question 28

Why do most food chain only have 4-5 trophic levels

Answer 28

Inefficiency of energy transfer means
- insufficient energy available to support a large enough breeding population a tighter TLS
- biomass less a tighter TLS
- total amount energy available les at each TLS